86 951 Driver

Did you try cleaning your MAF?

Clown

No I guess not. How do you clean a Maf? The filter?

MooreBoost

maf (sensor) cleaner

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_x_7070079-P_x_x?cm_mmc=ACQ-_-Google-_-enhancedRM-_-7070079&ci_src=17588969&ci_sku=7070079&ci_gpa=pla&ci_kw={keyword}&gclid= COOT6qnhwrMCFYYWMgodtR0A0w

blown 944

If it is missing due to spark it may show up as lean... Just saying

Rogue_Ant

Yep, spark-blowout looks like a lean-condition on a WBO2.

lee101315

Just curious here, Joshua and Sid...

Could you explain why a misfire would show up as lean on a WB02?

Thinking logically, if the spark isnt strong enough for whatever reason, you have an incomplete combustion which sends unburnt fuel into the exhaust system. I assume that misfire would cause a rich situation in the exhaust, as i've observed on engines misfiring slightly at idle ( narrow band 02s reading steadily around .6-.8 V )

Thanks

Rogue_Ant

The thing to remember is that O2 sensors measure oxygen content in the exhaust, not fuel content...
So incomplete combustion would have an excess of oxygen in the exhaust, because it wasn't used in combustion. The O2 sensor will see this 'extra' oxygen, and therefor display an enlean end condition.

Black51

Definitely sounds like a spark issue. My car's done the exact same thing in the past.

vette951s

Could also be a too cold a heat range of spark plug.

joker2cv

What could cause a weak spark except wires, distributor cap and rotor and coil?

Paulyy

Your ignition system is:
- Coil
- Cap & Rotor
- Leads
- Spark Plugs

Your computer is not part of an ignition system, just controls it..

Any of the 4 will cause a weak spark if not operating properly.

joker2cv

I'm using Bosch WR5DC+ spark plugs in my stock 951S: which gap is the best? I have some hesitation at partial throttle at low boost (4-6 psi) and AFR is about 13,5...

lee101315

Thanks for clearing that up Josh

jlturpin

Why are you running 5's? 7's should be good unless you are running over 18 pounds. What are they gapped at? Sounds like you may need to open the gap a bit if you are having running issues at low load. Also could be dirty or weak injectors, or if you are running super lean.

Chris White

Yes, too lean at boost I saw 14:1 at 15psi – but remember that if you have an ignition miss you will see higher O2 content in the exhaust due to unburnt fuel and air. So don’t be misled by the high AFR numbers – it still can be an ignition problem.